The present invention relates to a semiconductor device, and a method for fetching data, and in particular, to a semiconductor device including a switching circuit for repeating periodical ON/OFF, and a method for fetching data thereof.
In order to meet requirements for miniaturization of a semiconductor device, lower power consumption, and so forth, a power source making use of the switching circuit for repeating periodical ON/OFF, the so-called switching power source, has lately been in heavy use. For example, a dc-to-dc (DCDC) converter, and so forth are well known, the DCDC converter making use of a pulse width modulation (PWM) control for adjusting a duty ratio of a pulse signal inputted to the switching circuit.
With the use of the DCDC converter described as above, a supply voltage can be controlled according to an operation state of, for example, an electronic device. Further, such a DCDC converter as described, serving as a power management IC (PMIC: Power Management Integrated Circuit) can be formed in a chip to be mounted in a variety of electronic devices in order to reduce power consumption. Further, a similar switching technology is adopted in a class-D amp for driving a speaker in various electronic devices.
On the other hand, with the switching circuit, there occurs a power-source noise accompanying ON/OFF of a switch. Accordingly, countermeasures for preventing a malfunction caused by the power-source noise will be required. Needless to say, with the switching circuit, strenuous efforts have been underway in order to reduce the power-source noise by use of various noise filters and a decoupling capacitor. However, results have been unsatisfactory.
In Japanese Unexamined Patent Publication No. 2000-004147, there is disclosed a technology for removing a glitch noise contained in an asynchronous signal by use of an input circuit. Further, in Japanese Unexamined Patent Publication No. 2000-163173, there is disclosed a technology for reducing noise by staggering respective output timing of a signal and noise because the noise will increase if the signal and the noise are concurrently outputted from an output buffer of a digital circuit.